kreynolds

I started having a fuel pressure issue a couple of days ago and wanted to get some input from you guys. Back in June I installed my guages and found out I needed a new lift pump. Because I was limited on time, I picked up an airtex at the local parts house. I've been happy with it's performance so far. Up until two days ago I was seeing 17 psi at idle, 13-14 psi normal driving, 9 psi wot. Now my gauge tops out at 10-11 psi. This morning a changed the fuel filter but no change in psi. Now I'm starting to think my problem may be guage related. The guage climbs slowly at start up, used to be instantaneous. Also when driving I could not get it to drop below 9 psi. So I'm only seeing a 1 psi drop from top to bottom which doesn't seem right. I had to move it around this evening and I noticed that it took a minute for the pressure to drop to zero.
Ive got a mechanical isspro. It's tapped into the fuel line at the bottom of the fuel filter. The line runs from there to an isolator mounted on the firewall then up to the guage. I bleed the isolator when I changed out the filter today and none of my lines appear to be kinked anywhere.
Sorry for the long post, just looking for thoughts and suggestions. Thanks.

nuttynotty

Hay, Had a similar issue, where I was getting low pressure, changes the overflow valve, lift pump and filter, but still no joy, i have now found out that I'm sucking in air from somewhere, I'll be dropping the tank this weekend as when the tank is full she has good pressure, when only 1/4 tank left she is down in the 5psi .... Have you checked for air leaks ?

kreynolds

I've checked everything I can think of. I called Vulcan and spoke with a real nice guy. He thinks the problem is with the gauge. He was going to check with isspro to see about getting me a new one and call me back. I'm still waiting to hear back from him. Yesterday while I was driving the gauge just sat a 10 psi. This weekend I may take it out and reinstall just be sure I'm not missing something.

infidel

I've seen electrical gauges fail many times just as you describe but never a mechanical one.
That's the reason to use a mechanical, because you can trust it.

Sounds like the problem is a restriction somewhere in the line or isolator.
If you have a dampener or needle valve to dampen the pulses I would check to see if it's clogged.
You might want to try it without the isolator, they're nothing but trouble.

kreynolds

Seems we think alike. I'm gonna contact Vulcan again tomorrow and see if they have come anything. There was talk of possibly sending me a new gauge.

Russ Roth

I would be very suspicious of the isolator. Did you take the line off and push the diaphragm to the fuel side? If you did not that is very likely your problem. Been there done that. I use the eraser end of a pencil to push it over. Bet that will fix it. BTW, if that's it tell Adrian (or Eric) he should know that. Most likely Adrian.

kreynolds

I finally got a chance to undo some of the plumbing on my gauge. I found that my isolating fluid (glycol mixture) was gone. The tubing still had a green tint to it, but there was no fluid in the line or isolator. Refilled it and everything is back to normal. Wish I knew where it all went to as I haven't found any signs of a leak. I'm going to keep a close eye on it for a while. Or at least till i can plumb it direct to the gauge.

I have to say that I'm impressed with Vulcan's customer service. They sent out a new gauge after my initial call to them. Guess I'll be returning it, once it arrives.

Russ Roth

That's exactly what I was talking about. Been there done that. I'm surprised they did not have you check that first. My buddy has the same trouble with his isolator. I see where it's leaking but he lives about 2 hours away and he is not very mechanically inclined although he tries. It also gave him a hard start condition for some reason. Soon as he came by and I fixed it for about the third time, no more hard starts. Not sure how that worked. Vulcan has great customer service.